Raw water is oftentimes found to be in a quality level unacceptable as judged by health standards, on account of its undesirable contents such as toxic matter, pathogens and radioactive nuclides. In addition, such raw water may contain matter which can render it unsatisfactory with regard to palatability or appeal to the eye. Treatment measures to ameliorate water are usually applied by state, municipal authority, or by the individual consumer. These treatment measures typically include chemical, physical, and biological procedures that aim at eliminating undesirable suspended and dissolved matter. In U.S. Pat. No. 5,543,056 is disclosed a method for removing colour and particles, from drinking water by the use of chitosan in combination with a clay mineral. Chitosan is a derivative of chitin which is a natural polymer consisting of chains of acetylated glucosamine, usually extracted from shells of marine crustaceans. Chitosan is a fully or partially deacetylated chitin, wherein the naturally occurring amido bonds are hydrolyzed, leaving the amino groups of the polymer exposed and active.
Despite municipal or state treatment measures, resultant water is often not considered a reliable source for drinking water. Thus, concerned consumers opt for purchased canned or bottled water in order to ensure reasonable quality drinking water. However, bottled water are relatively expensive and may contain industrial contaminants derived from the walls of the container, in addition to the original natural impurities.
Several types of domestic water treatment systems are known in the art. Some rely on directly applied external energy for treating the water, for example distillation devices and ultraviolet irradiators. Other systems employ physical and or chemical processes that do not consume direct external energy. Among these some employ ion exchangers for eliminating ions such as calcium and other metal ions, and others employ activated carbon for mainly eliminating organic matter, dissolved gases and toxic materials; nevertheless some systems employ both ion exchangers and activated carbon. U.S. Pat. No. 4,717,476 discloses an apparatus for purifying water that employs a sequence of purification steps, each step accomplishes a different aspect of purification in a separate unit such that in the final step a desired product is obtained. U.S. Pat. No. 4,749,481 discloses a device and method for upgrading water quality for household use by using small, disposable disc-like elements that contain active material. These discs can be used in stacks thus performing successive steps of water treatment, each by a different disc element in the stack.
Home appliances for ameliorating consumer water are available in the market, that require connection to the home inlet, thus benefiting from the pressurized water supply provided by the local authorities. The pressure is used to drive the water through one or more cartridges that contain ion exchangers, and or activated carbon. Manufacturers of such devices recommend replacement of cartridges on a regular basis as well as other components of these systems that deteriorate in time. Other home appliances which do not require connection to the home plumbing, are pour—through water pitchers, typically containing cation exchange resins and activated carbon granules in their filters. Such filters often contain silver for preventing the build up of bacterial colonies, and generally require regular replacement. Some home water purifying systems contain easily replaceable parts so as to allow easy maintenance by the owner. In U.S. Pat. No. 5,989,424 the replaceable component is a filter cartridge.